Multichannel imaging using diffractive optics

摘要

ple imaging system can produce a two-dimensional array of images from a single input object. The basic components of our implementation are a high-performance Fourier processor and a suitably designed diffraction grating that is placed in the frequency phase. We have made use of a single diffractive element Fourier transform lens, corrected for coma, astigmatism, and field curvature. The lens is designed to have the proper amount of distortion to produce an optical transform. The optical processing system consists of two of these lenses spaced a distance equal to the sum of their focal lengths. We employ an iterative algorithm to produce the necessary phase diffraction grating that generates a multiplicity of equal energy plane waves from a single incident plane wave. The method is based on an iterative Fourier-transform scheme that makes use of known constraints to synthesize the phase structure. The constraints include the known Fourier modulus (array of point sources), the phase-only requirement in the grating plane, and fabrication requirements such as discrete phase levels. The iterative algorithm provides an efficient means to calculate grating profiles that give rise to large arrays of images. System performance over a relatively wide field-of-view is characterized by calculating the modulation transfer function at various points in the image plane.